TV broadcasting which converts and transmits high definition image signals (for example, hi-vision image signals) as digital signals has been in service for several years (hereinafter also “digital broadcasting”). This system change has resulted in the popularity of large, flat, high definition screen television receivers (hereinafter, “digital TVs” or simply “TVs”).
The system change has also resulted in the popularity of record-and-playback devices and optical disc playback devices. The record-and-playback devices can receive digital broadcasting, and record received signals in optical or magnetic discs to play them back. The optical disc playback devices can play back optical discs in which high definition image signals are recorded as digital signals. The record-and-playback devices and the optical disc playback devices are hereinafter uniformly referred to as “moving-image playback devices”.
Digital TVs can display high definition image signals played back by the moving-image playback devices without degradation by using high-definition multimedia interface (HDMI). HDMI is a growing standard for transmitting digital signals between a moving-image playback device and a digital TV.
The HDMI standard has a version with a feature called consumer electronics control (CEC), which enables devices connected via HDMI to exchange control signals. This version is hereinafter referred to as “HDMI-CEC”. HDMI-CEC compliant devices can be connected through an HDMI-CEC cable. When connected to each other via HDMI-CEC, devices not only can transmit and receive digital data to/from each other, but also can control each other: one device can control the other device, and vice versa. For example, when the user turns on a TV, the TV can transmit a control signal to a moving-image playback device connected to the TV, thereby turning the moving-image playback device on. As another example, when the user plays back a moving image on a moving-image playback device, moving-image playback device can transmit a control signal to a TV connected to the device. Then, in the TV, an input signal selection switch is selected, allowing the TV to display the moving image outputted from the moving-image playback device.
Infrared rays remote controls (hereinafter, “IR remote controls”) are now commonly used with controlled devices such as TVs and moving-image playback devices in order to transmit a control signal to the controlled devices via infrared. In general, each IR remote control in one-to-one correspondence with a controlled device. Therefore, when the user uses a plurality of such devices, the same number of IR remote controls is needed. This requires the user to take the trouble to select and pick up the appropriate IR remote control every time he/she remote controls one of the devices.
To solve this problem, there has been proposed a technique (see, for example, PTL1) in which a first device (for example, TV) includes an infrared transmission device for controlling a second device (for example, moving-image playback device) connected to the first device. The second device is controlled by using an IR remote control which is corresponded to the first device.
Infrared transmission devices are gradually being replaced by radio frequency remote controls (hereinafter, “RF remote controls”), which transmit and receive data to/from controlled devices using high-frequency radio waves (for example, in the 2.4 GHz band).
RF remote controls have the following advantages over IR remote controls.
capable of transmitting larger amounts of data
capable of performing bidirectional data communication (RF remote controls not only can transmit data to a controlled device, but also can receive data from the controlled device)
being more resistant to obstructions and blockages (RF remote controls can operate controlled devices regardless of the presence of some obstructions or blockages, whereas IR remote controls cannot if there is an obstruction or blockage)
having less limitations in the direction of use (being less directional) (RF remote controls can operate controlled devices even if not directed to the controlled devices. This is because an RF remote control transmits communication radio waves using an antenna embedded therein, and a controlled device receives the communication radio waves using an antenna embedded therein. An IR remote control, on the other hand, has to be pointed to a controlled device such that the light-emitting device of the IR remote control transmits infrared light to the light receiver of the controlled device)
As described above, RF remote controls are resistant to obstructions and blockage, and not very directional. These features, however, may cause radio waves from an RF remote control to be concurrently received by a plurality of devices. To prevent this malfunction, each RF remote control is corresponded to each controlled device. This is called “pairing” (see, for example, PTL2).
The pairing is generally performed as described from 1 to 5 below. Note that each RF remote control and each controlled device are previously assigned with unique information, which is an identification code (hereinafter, “ID” or “ID code”). The ID code can be, for example, a media access control (MAC) address.
1. An RF remote control transmits to a controlled device a “pairing request code”, which requests the execution of a pairing.
2. The controlled device receives the pairing request code, and then transmits its own ID code to the RF remote control.
3. The RF remote control receives the ID code of the controlled device, and then transmits its own ID code to the controlled device.
4. The controlled device receives the ID code of the RF remote control, and then transmits an acknowledge code (hereinafter, “ACK code”) to the RF remote control, the ACK code indicating the successful receipt of the ID code of the RF remote control. The controlled device then registers the ID code of the RF remote control as the ID code of the pairing partner.
5. The RF remote control receives the ACK code, and then registers the ID code of the controlled device as the ID code of the pairing partner.
Thus, the RF remote control and the controlled device are corresponded to each other by exchanging and registering their ID codes. After the execution of the pairing, the RF remote control transmits control data containing its own ID code and the ID code of the controlled device to the controlled device. The controlled device receives only control data that contains both its own ID code and the ID code of the RF remote control registered by the pairing, and ignores the other control data. As a result, the controlled device receives only the control data containing its own ID code transmitted from the RF remote control of the pairing partner. This prevents the above-described malfunction where a plurality of devices operate concurrently.
Once paired, the RF remote control and the controlled device are maintained in one-to-one correspondence with each other unless the user erases the ID code registered in the RF remote control or the controlled device (for example, by initialization). Therefore, it is unnecessary to redo a pairing unless the ID code is erased.
As described above, devices connected via HDMI-CEC can control each other. Therefore, it is possible, when a first device is paired with an RF remote control, and is connected to a second device via HDMI-CEC, to remote control the second device by way of the first device using the RF remote control. This allows the user to remote control both first and second devices using one RF remote control, making this system more user-friendly. It takes more time for the user, however, to remote control the second device by way of the first device, than to remote control the second device using an RF remote control paired with the second device.
Alternatively, it is possible to pair the RF remote control paired with the first device further with the second device, allowing the user to remote control both first and second devices using one RF remote control. This, however, requires the user to take the trouble to pair the RF remote control paired with the first device further with the second device.